Thanks, that's a nice read! (Note that I never suggested that CSS creators were unaware of the TeX box model, though I had no idea to what extent was it considered early on)

That also supports my claim that reflowing in TeX's box model would be simpler ("CSS is richer").

I simply highlighted a few things where TeX's box model does a great job for what are commonly hard problems with CSS even today (how do you align columns on decimal points?): I imagine most people, even LaTeX users today, are unaware of the internals, and I hope it's valuable for people to learn of them.